A tunnel-junction magnetoresistive (TuMR) element includes a fixed magnetization layer and a free layer. The fixed magnetization layer is configured to fix the direction of magnetization even under the influence of an external magnetic field. The free layer is configured to change the direction of magnetization under the influence of an external magnetic field. The fixed magnetization layer includes a pinned layer, a reference layer and a non-magnetic layer sandwiched between the pinned layer and the reference layer. A tunnel barrier layer is sandwiched between the fixed magnetization layer and the free layer. The magnetoresistance of the tunnel-junction magnetoresistive element changes depending on a relative angle between the direction of the magnetization of the fixed magnetization layer and that of the free layer. Variation in the magnetoresistance is utilized to discriminate binary data.
The tunnel-junction magnetoresistive element has a so-called bottom type multilayered structure. The fixed magnetization layer is received on an antiferromagnetic layer in the bottom type multilayered structure. The antiferromagnetic layer is made of IrMn (iridium manganese), for example. The IrMn layer tends to suffer from unevenness of a relatively large scale on the surface based on crystal grains. The unevenness of the antiferromagnetic layer affects the tunnel barrier layer through the pinned layer, the non-magnetic layer and the reference layer formed on the antiferromagnetic layer. This results in deterioration in magnetic interaction established between the free layer and the reference layer.    Publication 1: IP Patent Application Laid-open No. 2007-294737    Publication 2: IP Patent Application Laid-open No. 2008-103661
A so-called top type multilayered structure is proposed for the tunnel-junction magnetoresistive element to eliminate such deterioration. The top type multilayered structure includes a free layer, a tunnel barrier layer, a reference layer, a non-magnetic layer, a pinned layer and an antiferromagnetic layer overlaid on one another in this sequence. The antiferromagnetic layer is layered in the tunnel-junction magnetoresistive element after the establishment of the tunnel barrier layer. The tunnel barrier layer is thus released from the effect of the unevenness of the antiferromagnetic layer. However, the top type multilayered structure inevitably suffers from a reduction in a resistance to the external magnetic field. As a result, variation in the magnetoresistance becomes small. Sensitivity deteriorates for reading binary data.